Some of the heaviest fighting took place in Beit Hanoun in the northern Gaza Strip, where sounds of explosions, machine gun fire and helicopter gunships could be heard for miles.

Since Israel pulled out of the Gaza Strip in August 2005, Iranian-backed terrorists, led by Hamas, have fired more than 6,000 rockets on Israeli communities near Gaza.

And they've shown in the past week that the rocket range has expanded to put many more Israeli lives in danger.

Israel's military command called up tens of thousands of reserve soldiers to join the operation if needed.

While leaving family, jobs and friends isn't easy, reserve soldiers, who serve a yearly stint through age 40, understand it's their duty.

"I feel afraid a little bit, but what can we do," one reservist said. "This is the situation and we need to defend ourselves," he said.

On Sunday, friends and family mourned at the funeral of Staff Sgt. Dvir Emanueloff, 22, the first Israeli soldier killed in the Gaza ground operation.

According to international estimates, more than 500 Palestinians have died in eight days of air and ground strikes. Most of them are from Hamas's military wing.

Israeli leaders know their window for ground action may be limited. As international protests against Israel grow, the leaders of Britain and France have called for an immediate cease-fire, and the United Nations Security Council will take up the issue again on Tuesday.

But the last thing Israel needs is an operation that fails to stop Hamas from threatening Israel again.

"We were faced with a Hamas regime that tore up the cease-fire, that initiated rocket barrage after rocket barrage against our civilian population in the south, and we are forced to act to defend our people," Israeli government spokesman Mark Regev said.

Meanwhile, The Jerusalem Post reports that Hamas gunmen have shot 75 rival Fatah members in the legs, allegedly to prevent Fatah from challenging Hamas control in the Gaza Strip.

Hamas has also executed at least 35 Palestinians as "collaborators" with Israel.